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Appendix Exh7-14D <br /> Section 16 Fill Ditch <br /> The Section 16 Fill Ditch is located in the SE1/4 of Section 16 of T3N, R93W. The alignment of <br /> this ditch is shown on Map 41. The ditch conveys a very small area of Section 16 reclamation <br /> areas into the South Collection Ditch ultimately reporting to the Prospect Pond drainage system. <br /> The ditch is designed to meet the requirements of Rule 4.05.3 for drainages less than one square <br /> mile. The drainage area of this basin is about 12.4 acres, all of which is now Phase III released. <br /> The steepest portions have a slope of about 17.8 percent. The overall length of the channel is <br /> about 860 feet. <br /> As shown on the attached SEDCAD model, the design storm produces a peak discharge of about <br /> 1.77 cfs. Part of the design event is based on a Curve Number of 74, as the appropriate curve <br /> number of 47 did not generate enough flows for the model work appropriately. <br /> Because the flow is so small, the design has been based on a triangular ditch(zero bottom width) <br /> with 3H:1 V side slopes, but as a construction expedient, the ditch may have a bottom width up to <br /> 12 feet based simply on the minimum width of a dozer blade. Rip-rap protection is provided, <br /> with a D50 of 12 inches as calculated in the attached SEDCAD model using the Simons/OSM <br /> method for sizing rip-rap. <br /> A road traverses across the Section 16 Fill Ditch near station 1+85, which provides access to <br /> maintain power line infrastructure in the area. A culvert is installed and maintained in the <br /> Section 16 Fill Ditch, but it is not a Colowyo mining related structure. Please see Volume 1, <br /> Section 4.12 for a further discussion. The culvert is modeled even though it is not a Colowyo <br /> culvert to ensure it is sized appropriately. <br /> Given that, the peak storm discharge of 1.77 cfs requires a minimum of one 12" culvert is <br /> necessary in the Section 16 Fill Ditch. However, one 24" culvert is installed, which will more <br /> than suffice for the flows generated by the Section 16 Fill Ditch. <br /> Exh. 7-14D-2 Revision Date: 1/22/20 <br /> Revision No.: TR-136 <br />